Process for preparing liquid crystalline polymer composites

ABSTRACT

This invention provides an optical medium which consists of a composite of a homogeneous inorganic oxide glass monolith with a microporous structure containing a liquid crystalline polymer component. 
     In one embodiment this invention provides a sole-gel process for producing a composite of a transparent homogeneous microporous inorganic oxide glass monolith and a liquid crystalline polymer.

This application is a division of application Ser. No. 015,758 filedApr. 10, 1987, now U.S. Pat. No. 4,828,888.

BACKGROUND OF THE INVENTION

Liquid crystalline materials are utilized in a variety of electroopticaland display device applications, in particular those which requirecompact, energy efficient, voltage-controlled light valves such ascalculator displays.

Illustrative of organic materials which exhibit liquid crystallinebehavior are (1) relatively stiff elongated molecules such as4,4'-azoxyanisole; (2) polymers which are wholly aromatic in structuresuch as a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoicacid; and polymers with a flexible main chain and with side chains whichexhibit mesogenic properties.

Low molecular weight liquid crystalline compounds exhibit opticalproperties while in the liquid mesogenic phase. Liquid crystallinepolymers exhibit a thermotropic mesophase, and have the additionaladvantage that the optical properties can be preserved in the solidstate.

As a further embodiment, liquid crystalline compounds have beenincorporated as minute droplets in a porous polymeric matrix to protectthe reactive material from atmospheric conditions and to enhanceelectric field behavior. Polymeric encapsulated liquid crystallinematerials are described in U.S. Pat. Nos. 3,600,060; 4,048,358; and4,579,423.

While the encapsulation of a liquid crystalline material in a polymericmatrix has desirable advantages, there are disadvantages associated withthis type of composite structure. The polymer tends to cause spectralshifts of both absorption and emission wavelengths, and it can affectthe photostability of the liquid crystalline material, and typically thepolymeric matrix does not have a broad range of optical transparency.

Of background interest with respect to the present invention is JapanesePatent 73JP-098101 which describes a thermal type liquid crystal displaydevice which consists of (1) a porous glass structure prepared byheating borosilicate glass to cause separation of phases, and leachingthe boron oxide-rich and sodium oxide-rich phase with sulfuric acid toform a silica-rich porous glass; (2) a liquid crystal material in thepore volume; (3) a heating element coated on the porous glass in apattern, and (4) a transparent protective cover.

Other publications of interest which describe the production ofinorganic-organic composites are J. Phys. Chem., 88, 5956 (1984) and J.Non-Cryst. Solids, 74, 395 (1985) by D. Avnir et al, and Mat. Res. Soc.Symp. Proc., 73, 809 (1986) by Pope et al; incorporated herein byreference.

There is continuing interest in the development of improved liquidcrystalline materials and structures which exhibit exceptionalproperties for specialized applications.

Accordingly, it is an object of this invention to provide novel liquidcrystalline polymer composites.

It is another object of this invention to provide a transparent opticalmedium which is a solid composite of a homogeneous porous inorganicoxide glass and a liquid crystalline polymer component with enhancedphotostability.

It is another object of this invention to provide a process forproducing novel liquid crystalline polymer composites.

It is a further object of this invention to provide optical deviceswhich contain a novel liquid crystalline polymer composite opticalcomponent.

Other objects and advantages of the present invention shall becomeapparent from the accompanying description and examples.

The subject matter of this patent application is related to thatdisclosed in copending patent application Ser. No. 15,757, filed Apr.10, 1987, now U.S. Pat. No. 4,814,211, and copending patent applicationSer. No. 15,758, filed Apr. 10, 1987, now U.S. Pat. No. 4,828,888.

DESCRIPTION OF THE INVENTION

One or more objects of the present invention are accomplished by theprovision of an optical medium comprising a composite composition of ahomogeneous inorganic oxide glass monolith with a microporous structurecontaining a liquid crystalline component.

The glass monolith typically is comprised of silica either alone or incombination with up to about 20 weight percent of one or more otherinorganic oxides of elements such as lithium, sodium, potassium,rubidium, cesium, magnesium, calcium, strontium, barium, titanium,zirconium, vanadium, tantalum, chromium, molybdenum, tungsten,manganese, iron, nickel, cobalt, copper, zinc, cadmium, boron, aluminum,phosphorus, gallium, germanium, tin, arsenic, antimony, bismuth,selenium, and the like.

A present invention glass monolith microporous structure nominally has apore volume between about 10-80 percent of the total volume, and haspore diameters in the range between about 15-2000 angstroms. The averagepore diameter typically is in the range between about 50-300 angstroms.

The glass monolith can be in the form of thin coatings on transparent orreflective substrates; films; plates; cubes; cylinders; prisms; fibers;and the like.

The liquid crystalline component can occupy between about 1-99 percentof the microporous volume of the glass monolith, and usually it occupiesbetween about 5-95 percent of the microporous volume.

The liquid crystalline component can be homogeneously distributedthroughout the microporous volume. In another embodiment the liquidcrystalline component is concentrated in a zone of the microporousstructure which is adjacent to a surface of the glass monolith. As analternative, the glass monolith can have microporosity in one or morezones, and the microporous volume of a zone contains liquid crystallinecomponent.

In another embodiment the content of the liquid crystalline componenthas a gradient distribution in the microporous structure of an inventionglass monolith.

In another embodiment this invention provides a transparent opticalmedium which is coated on a transparent or reflective substrate, whereinthe optical medium is a composite composition comprising a homogeneousinorganic oxide glass monolith with a microporous structure containing aliquid crystalline component.

In another embodiment this invention provides an optical light switch orlight modulator device with an optical medium component comprising acomposite composition consisting of a homogeneous inorganic oxide glassmonolith with a microporous structure containing a liquid crystallinecomponent.

In another embodiment this invention provides a transparent opticalmedium which is in the form of a thin sheet having a thickness less thanabout 2 millimeters and which has each side surface coated with atransparent electrically conductive film, wherein the optical medium isa composite composition comprising a homogeneous inorganic oxide glassmonolith with a microporous structure containing a liquid crystallinecomponent.

The term "transparent" as employed herein refers to an optical mediumwhich is transparent or light transmitting with respect to incidentfundamental light frequencies and created light frequencies. In anoptical device, a present invention liquid crystalline composite opticalmedium is transparent to both the incident and exit light frequencies.

Preparation Of Porous Inorganic Oxide Glass Monoliths

The various methods for the manufacture of porous glass are reviewed inU.S. Pat. No. 4,528,010. The methods include the Vycor (Corning),chemical vapor deposition, white carbon, colloid silica, and silica gelprocedures.

One method of producing a porous glass body involves (1) forming anarticle of desired shape from a parent borosilicate glass; (2) thermallytreating the glass article at a temperature of 500°-600° C. to separatethe glass into a silica-rich phase and a silica-poor phase; (3)dissolving or leaching the silica-poor phase with acid to provide aporous structure composed of the silica-rich phase; and (4) washing toremove leaching residue, and then drying.

Embodiments for production of porous inorganic oxide glass monoliths byleaching of a soluble phase from a solid glass structure are describedin U.S. Pat. Nos. 2,106,744; 2,286,275; 2,303,756; 2,315,328; 2,480,672;3,459,522; 3,843,341, 4,110,093; 4,112,032; 4,236,930; 4,588,540; andreferences cited therein; incorporated herein by reference.

U.S. Pat. No. 4,584,280 describes a process for preparing a transparentporous ceramic film which involves applying an anhydrous solutioncontaining an organometallic compound and a multifunctional organiccompound to a substrate; and then thermally decomposing the organiccompounds.

A more recent development is the "sol-gel" process for preparation ofporous monolithic glasses and ceramics at moderate temperatures. Thesol-gel procedure involves the formation of a three-dimensional networkof metal oxide bonds at room temperature by a hydrolysis-condensationpolymerization reaction of metal alkoxides, followed by low temperaturedehydration. The resultant porous glass structure optionally can besintered at elevated temperatures.

In another embodiment this invention provides a process for producing acomposite composition comprising a homogeneous inorganic oxide glassmonolith with a microporous structure containing a liquid crystallinecomponent, which comprises hydrolyzing tetraalkoxysilane under acidic orbasic pH conditions in a sol-gel reaction medium comprising water, awater-miscible organic solvent and a liquid crystalline component, untilgellation of the reaction medium is completed, and removing the solventmedium to provide a porous glass monolith with incorporated liquidcrystalline component.

In another embodiment this invention provides a process for producing acomposite composition comprising an inorganic oxide glass monolith witha microporous structure containing a liquid crystalline component, whichcomprises (1) hydrolyzing tetraalkoxysilane under acidic or basic pHconditions in a sol-gel reaction medium comprising water and awater-miscible organic solvent until gellation of the reaction medium iscompleted; (2) removing the solvent medium to provide a porous glassmonolith; and (3) impregnating the porous glass monolith with a liquidcrystalline component.

The term "homogeneous" as employed herein with reference to a porousglass monolith means that the inorganic oxide composition and themicrostructure are substantially invariant throughout the monolith.

Embodiments for production of porous inorganic oxide glass monoliths bythe sol-gel process are described in U.S. Pat. Nos. 3,640,093;3,678,144; 3,681,113; 3,811,918; 3,816,163; 3,827,893; 3,941,719;4,327,065; 4,389,233; 4,397,666; 4,426,216; 4,432,956; 4,472,510;4,477,580; 4,528,010; 4,574,063; and references cited therein;incorporated herein by reference. Mat. Res. Soc. Symp. Proc., 73, 35(1986) by Hench et al describes the role of chemical additives insol-gel processing; incorporated herein by reference.

Illustrative of water-miscible solvents employed in a sol-gel processembodiment are alkanols such as methanol and ethanol; ketones such asacetone and methyl ethyl ketone; esters such as methyl acetate and ethylformate; ethers such as dioxane and tetrahydrofuran; amides such asdimethylformamide, dimethylacetamide and 1-methyl-2-pyrrolidinone; andthe like.

Acidic pH conditions in the sol-gel process can be provided by theaddition of mineral acids such as hydrochloric acid, and basic pHconditions can be provided by the addition of bases such as ammoniumhydroxide.

Illustrative of tetraalkoxysilanes and other metal and metalloidalkoxides are methoxy and ethoxy derivatives of silicon, lithium,magnesium, titanium, manganese, aluminum, tin, antimony, and the like.Aryloxy derivatives also can be utilized in the sol-gel process.

Porous glass monoliths produced by a sol-gel process embodiment have anadvantageous combination of properties, and generally have superioroptical properties as compared to porous glass monoliths prepared byother techniques, e.g., by the leaching of a silica-poor phase from aborosilicate glass.

A sol-gel derived porous glass monolith is homogeneous and the inorganicmatrix can be obtained essentially free of inorganic or organicimpurities, e.g., less than 2 weight percent of impurities.

A sol-gel derived porous glass monolith typically has a pore structurein which substantially all of the pores have diameters within about a100 angstrom diameter variation range, e.g., within a range betweenabout 50-150 or 300-400 or 900-1000 angstroms, as determined by sol-gelprocessing conditions.

A sol-gel derived porous glass monolith can have exceptional opticalproperties because the inorganic matrix is homogeneous in chemicalcomposition and physical structure. Since there is minimized lightscattering, the sol-gel derived porous glass monolith exhibits excellentoptical transparency and light transmitting ability.

Liquid Crystalline Component

The liquid crystalline component of the invention composite compositionscan be selected from a broad variety of known compounds, oligomers andpolymers which exhibit smectic, nematic and/or cholesteric mesophases.

The mesophase temperature can vary in the broad range between about0°-150° C., depending on the chemical structure of a particular liquidcrystal component. Mixtures of liquid crystals can be employed toprovide a medium which has a mesophasic state at ambient temperatures.

The liquid crystalline component also can be employed in combinationwith an organic dye, such as anthraquinone dye D-16 (B.D.H. Chemicals)and azo dye GR-8 (Japan Photosensitive Pigment Research Institute).

Various classes of liquid crystalline compounds are described in U.S.Pat. Nos. 3,322,485; 3,499,702; 4,032,470; 4,105,654; 4,228,030;4,323,473; 4,382,012; 4,556,727; 4,576,732; 4,592,858; 4,550,980;4,601,846; and references cited therein; incorporated herein byreference.

The liquid crystalline component of the invention composite compositionalso can have a polymeric structure. Illustrative of this class oforganic materials is a liquid crystalline polymer which is characterizedby a recurring wholly aromatic structural unit corresponding to theformula:

    Ar--X--Ar--

where X is a divalent radical selected from estero, amido, azomethino,azo, azoxy, etheno and ethyno groups, and Ar is a divalent aromaticradical selected from phenylene, naphthylene and diphenylene groups, andaromatic radicals corresponding to the formula: ##STR1## where Y is acarbonyl, sulfono, oxy or thio group.

Illustrative of a wholly aromatic liquid crystalline polymer componentis a copolymer of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid.

The term "wholly aromatic" as employed herein refers to a linearthermotropic liquid crystalline polymer in which each recurringmonomeric unit contributes at least one aromatic nucleus to the polymerbackbone.

The term "thermotropic" as employed herein refers to polymers which areliquid crystalline (i.e., anisotropic) in the melt phase.

Wholly aromatic thermotropic liquid crystalline polymers are disclosedin U.S. Pat. Nos. 3,526,611; 3,991,013; 4,048,148; 4,057,597; 4,066,620;4,067,852; 4,075,262; 4,083,829; 4,107,143; 4,118,372; 4,122,070;4,130,545; 4,146,702; 4,153,779; 4,156,070; 4,159,365; 4,161,470;4,169,933; 4,181,792; 4,184,996; 4,188,476; 4,219,461; 4,224,433;4,230,817; 4,238,598; 4,238,599; 4,256,624; 4,332,759; and 4,381,389;incorporated herein by reference.

Another type of liquid crystalline polymer is illustrated by a sidechain liquid crystalline polymer which is characterized by a recurringstructural unit corresponding to the formula: ##STR2## where P is apolymer main chain unit, S is a flexible spacer group having a linearchain length of between about 1-20 atoms, M is a pendant mesogen, andwhere the pendant mesogens comprise at least about 10 weight percent ofthe polymer and the polymer has a glass transition temperature aboveabout 40° C.

Side chain liquid crystalline polymers are disclosed in U.S. Pat. Nos.4,293,435; 4,358,391; and 4,410,570; incorporated herein by reference.

Other literature describing side chain liquid crystalline polymersinclude J. Polym. Sci., 19, 1427 (1981); Eur. Polym. J., 18, 651 (1982);Polymer, 26, 615 (1985); incorporated herein by reference.

Liquid crystalline polymer technology is reviewed in "Polymeric LiquidCrystals", (Plenum Publishing Corporation, New York, 1985), and in"Polymer Liquid Crystals" (Academic Press, New York, 1982); incorporatedherein by reference.

External Field Induced Liquid Crystal Orientation

The term "external field" as employed herein refers to an electric ormagnetic field which is applied to a substrate of mobile organicmolecules, to induce dipolar alignment of the molecules parallel to thefield.

Liquid crystals (including polymeric liquid crystals) may be aligned bythe application of an external field to a matrix of liquid crystalmolecules. The degree of orientation is determined by the orientationalorder parameter. For both nematic and smectic mesophases, the parameteris defined in terms of a director which is a vector parallel to themolecular long axis (and perpendicular to the plane of molecularlayering in the case of the smectic mesophase).

If theta is defined as the angle between the director and a chosen axis,then the orientational order parameter is defined as the average overall molecules of the second Legendre polynomial. The parameter rangesfrom -0.5 to 1.0 (1.0 corresponds to perfect uniaxial alignment along agiven axis. 0.0 corresponds to random orientation, and -0.5 correspondsto random orientation confined in a plane perpendicular to a givenaxis).

The order parameter thus defined does not distinguish between paralleland antiparallel alignment. Thus, a sample of asymmetric rod-likemolecules would have an order parameter of 1.0 for both the case inwhich the molecules are colinear and all pointed in the same direction,and the case in which the molecules are colinear and form antiparallelpairs.

The application of an orienting external field to an array of nematicliquid crystal molecules results in an order parameter of approximately0.65. Deviations from ideal order are due to nematic fluctuations on amicron length scale which accommodate characteristic defects. Thesefluctuations may be dynamic for small molecule liquid crystals or frozenfor polymeric liquid crystals. In either case, nematic fluctuationsscatter light so that aligned samples appear to be hazy (particularly ina thick sample).

Smectic liquid crystals may be aligned by application of an orientingexternal field, with a resulting order parameter exceeding 0.9. Unlikethe nematic phase, characteristic defects are removed upon aligning thesmectic phase and thereby forming a single liquid crystal phase. Suchphases are known as monodomains and, because there are no defects, areoptically clear.

For both the nematic and smectic mesophases, application of a DCelectric field produces orientation by torque due to the interaction ofthe applied electric field and the net molecular dipole moment. Themolecular dipole moment is due to both the permanent dipole moment(i.e., the separation of fixed positive and negative charge) and theinduced dipole moment (i.e., the separation of positive and negativecharge by the applied field).

The torque which results by the application of a DC electric fieldnormally would only produce very slight alignment even for high dipolarand polarizable molecules at room temperature. The alignment torque isnegligible in comparison with the disordering effect of thermallyinduced rotation (i.e., the Boltzman distribution of rotationaleigenstates at room temperature). However, due to the uniqueassociations developed by liquid crystalline molecules throughintermolecular forces, long range orientational order on a micron lengthscale is present. Under these conditions, bulk orientation of the sampleby application of aligning fields exceeding a few volts/cm can producethe degrees of alignment indicated above.

Application of an AC electric field also can induce bulk alignment. Inthis case, orienting torque occurs solely due to the interaction of theapplied AC field and the induced dipole moment. Typically, AC fieldstrengths exceeding 1 kV/cm at a frequency exceeding 1 KHz are employedfor the nematic phase. At these frequencies, rotational motion ofaligned nematic regions is not sufficient to follow the field. As adirect result, torque due to the interaction of the applied field andany permanent dipole moment over time averages to zero. However,electronically induced polarization is a very rapid process so that theinduced dipole moment changes direction depending upon the direction ofthe applied field resulting in a net torque.

Application of a magnetic field also can effect alignment. Organicmolecules do not possess a permanent magnetic dipole moment. In a manneranalogous to AC electric field, a magnetic field can induce a netmagnetic dipole moment. Torque results from the interaction of theinduced dipole moment and the external magnetic field. Magnetic fieldstrengths exceeding 10 Kgauss are sufficient to induce alignment for anematic phase.

Alignment of nematics by electric or magnetic fields are accomplishedsimply by application of the field to the nematic material. Alignment ofthe smectic phase is more difficult due to a higher viscosity whichdecreases rotational freedom. Formation of aligned smectic monodomainscan be achieved by orienting a material in the nematic phase, andcooling the material into the smectic phase while maintaining thealigning field. For materials which have only smectic and isotropicphases and which lack a nematic phase, alignment can be accomplished inthe smectic phase at an elevated temperature near the smectic toisotropic transition temperature, e.g., sufficiently close to thetransition temperature so that the medium may contain smectic domains inan isotropic fluid.

The methods described above to produce oriented materials apply to bothsmall molecule liquid crystals and polymeric liquid crystals. Forpolymers which possess a glass transition, the aligned liquidcrystalline phase can be frozen by rapid cooling below the glasstransition temperature.

Publications relating to external field-induced liquid crystal molecularorientation include The Physics of Liquid Crystals, P. G. deGennes, p.95-97, Oxford University Press, 1974; J. Stamatoff et al, "X-RayDiffraction Intensities of a Smectic-A Liquid Crystal", Phys. Rev.Letters, 44, 1509-1512, 1980; J. S. Patel et al, "A Reliable Method ofAlignment for Smectic Liquid Crystals: Ferroelectrics, 59, 137-144,1984; J. Cognard, "Alignment of Nematic Liquid Crystals and TheirMixtures", Mol. Cryst. Liq. Cryst.: Suppl., 1982; incorporated herein byreference.

A present invention composite of a sol-gel derived porous glass monolithand a liquid crystalline component exhibits unique optical properties.Because of the homogeneity of the inorganic monolith and the relativelysmall average pore size (e.g., 50-100 angstroms), the composite appearsoptically transparent either with random or with uniaxial orientedliquid crystalline molecules. The composite is characterized by veryfast and large electric field-induced birefringence.

It is believed that there are surface charges on the internal interfacesbetween the inorganic monolith phase and the liquid crystal phase. Thesesurface charges tend to restore each domain to its original direction ofalignment in the absence of an electric field.

The following examples are further illustrative of the presentinvention. The components and specific ingredients are presented asbeing typical, and various modifications can be derived in view of theforegoing disclosure within the scope of the invention.

EXAMPLE I

A section of porous glass (3 cm×3 cm×3 mm) of 40-50 angstroms averagepore diameter is submerged in a benzene solution containing 30% byweight of p-n-butoxybenzylidene-p'-aminobenzonitrile for one hour.

The impregnated glass section is withdrawn from the solution and driedunder vacuum at 60° C. to remove the benzene solvent from the porestructure. The porous glass product is transparent.

The porous glass product is film coated with poly(methyl methacrylate)by dipping the liquid crystal impregnated porous glass into a methylethyl ketone solution of poly(methyl methacrylate) and then air drying.

The above procedure is repeated, except that the impregnated porousglass is coated on both sides with transparent electronically conductiveindium-tin oxide.

In the absence of an electric field, the glass monolith is anon-scattering optical medium. Upon application of an electric fieldwhich aligns the liquid crystal molecules, the optical medium becomesbirefringent. When combined with cross-polarizers, the inducedbirefringence in the glass/liquid crystal composite is effective as alight filter.

EXAMPLE II

A starting solution for the production of thin films is prepared byadmixing 50 ml of ethanol, 50 ml of dioxane, 10 ml oftetramethoxysilane, 5 ml of 0.01N HCl, 3 g of Triton® X-100.sup.(1) and0.1 g of p-azoxyanisole. The solution is allowed to stand for two hoursat room temperature.

Glass slides are dipped into the solution, and then dried at 110° C. for10 hours. The resultant transparent film coating is a porous silicatemonolith containing pore volume encapsulated p-azoxyanisole component.

In an alternative procedure, the p-azoxyanisole is not included in thefilm preparation solution. After glass slides are coated with poroussilicate film, the glass slides are dipped into a benzene solution ofp-azoxyanisole to impregnate the porous film coating with the solution.After glass slides are dried to remove the solvent, the resultantcomposite coating on the glass slides is a transparent silicate filmwith a microporous structure containing incorporated p-azoxyanisole.

EXAMPLE III

A transparent porous ceramic thin film is prepared in accordance withthe procedure described in U.S. Pat. No. 4,584,280.

A 50 g quantity of tetraethoxysilane is dissolved in 100 g ofisopropanol, and 20 g of ethanol containing 2% of 1% aqueoushydrochloric acid solution is added dropwise with stirring. This isfollowed by the addition of 20 g of ethanol containing 3%hydroxyethylcellulose, and the mixture is refluxed for 15 minutes withstirring to provide a clear viscous solution.

The solution is spread on the surface of a thin stainless steel plateand dried at room temperature. The coated plate is heated in a mufflefurnace at a rate of 5° C./min, and maintained at 500° C. for one hour.After gradual cooling of the plate, a transparent thin film of silicateis evident on the stainless steel surface. The average pore size is inthe range of 40-60 angstroms.

The coated plate is dipped into a 20% tetrahydrofuran solution of agraft copolymer of 4-methoxyphenyl-4-(2-propenoxy)benzoate andmethylhydrogenpolysilane (as described in U.S. Pat. No. 4,358,391). Thecoated plate is dried at 100° C. to remove the solvent from the poroussilicate film. The resultant porous silicate film has a content ofincorporated liquid crystalline polymer.

EXAMPLE IV A.

A porous glass plate (10 cm×10 cm×1 cm) of 100-120 angstroms averagepore diameter is set in a shallow pan containing a 20% toluene solutionof 4,4'-dimethoxystilbene. The one centimeter sides of the glass plateare submerged to a depth of 3 millimeters. After 2 minutes of immersionin the solution, the glass plate is withdrawn and dried to remove thetoluene solvent. The resultant porous glass plate product has a4,4'-dimethoxystilbene content which is concentrated in a zone of themicroporous structure which is adjacent to one flat surface of the glassplate.

A similar product is obtained if the glass plate has porosity only in anarrow zone adjacent to one of the glass plate surfaces, and the porevolume is impregnated with a solution of liquid crystalline compound, orwith an isotropic melt phase of the liquid crystalline compound.

B.

A porous glass plate (6 cm×6 cm×2 cm) of 80-100 angstroms average porediameter is set in a shallow pan containing a 30% benzene solution of50/50p-n-ethoxybenzylidene-p'-aminobenzonitrile/p-n-butoxybenzylidene-p'-aminobenzonitrile(Crystal-nematic transition temperature of 41° C.) The 2 centimetersides of the glass plate are submerged to a depth of 2 millimeters.After 20 minutes of immersion in the solution, the glass plate iswithdrawn and dried to remove the benzene solvent.

The resultant porous glass plate product has a liquid crystallinecontent which has a gradient distribution in the microporous structure,from dense near one flat surface to less dense near the opposite flatsurface. The gradient distribution is the effect of solvent capillaryaction in the interconnected microporous structure during theimpregnation procedure.

What is claimed is:
 1. A process for producing a composite compositioncomprising a homogeneous inorganic oxide glass monolith with amicroporous structure containing a liquid crystalline component, whichcomprises (1) hydrolyzing tetraalkoxysilane under acidic or basic pHconditions in a sol-gel reaction medium comprising water and awater-miscible organic solvent until gellation of the reaction medium iscompleted; (2) removing the solvent medium by drying to provide a porousglass monolith; and (3) impregnating the porous glass monolith with aliquid crystalline polymer component; wherein the glass monolithmicroporous structure has pore diameters in the range between about15-2000 angstroms, and substantially all of the pore diameters arewithin about a 100 angstrom diameter variation range.
 2. A compositecomposition produced in accordance with the sol-gel process of claim 1.